14 years of solar eclipse chasing (and counting): a team travels the world to study solar wind
The solar system is constantly bathed by a sea of charged particles emanating from the sun, and a research team spent 14 years tracking solar eclipses to learn more about this star spray.
The particles are known as the solar wind and come from the outermost region of the sun: the corona. If a person is lucky enough to see a total solar eclipse, they will definitely see this pearly region around the sun. This delicate area has the visual charm of a cosmic halo but is in equal parts an inferno. The corona is the hottest region of the sun, reaching temperatures in excess of 2 million degrees Fahrenheit (more than 1 million degrees Celsius). The extreme temperature in this gaseous stellar cocoon has puzzled scientists, as this is a very different story from what happens 1,000 miles (1,600 kilometers) below the corona, where the temperature is significantly cooler to NASA.
Scientists want to understand the solar wind for many reasons. Solar wind defines the parameters of the solar system and sets its limits: Since the solar wind spreads more and more thinly with increasing distance from the sun, the particles cannot withstand the recoil from interstellar space. Much closer to Earth, solar wind protects us from dangerous cosmic rays, but can also disrupt space-based communication satellites and GPS systems.
connected: Solar Orbiter records its first video of an eruption on the sun
For the past 14 years, Shaddia Habbal, solar researcher at the University of Hawaii, has led a team to Oregon, Indonesia, Argentina, the Sahara in Libya, the Gobi Desert in Mongolia and many other places where solar eclipses occur. Their goal was to observe the solar corona for a slightly longer period of time than it takes for the sun to complete a cycle of solar activity, about 11 years. Total solar eclipses, which occur when the lunar disk blocks all sunlight except for the corona, are an important opportunity for researchers to observe the source of solar wind from Earth.
The team made high-resolution observations of 11 total solar eclipses with cameras equipped with special filters. With this device, the scientists were able to measure the temperatures of the particles from the innermost part of the corona, the birthplace of the solar wind. The researchers then compared their results with data from NASA’s Advanced Composition Explorer (ACE) mission, launched in 1997, which observes solar winds from a location in space about 1/100 the distance from Earth to the Sun.
During the Sun’s 11-year cycle, the star oscillates between dormant and volatile periods. When the sun is still, the star’s face has few sunspots. This is very different from the sun’s volatile season, when blemishes and solar flares are the order of the day.
connected: What’s in the sun? A start tour from the inside out
(Photo credit: NASA / NRL / STEREO / Karl Battams)
The radically different appearance of the sun over the course of the solar cycle made these scientists surprised to find that their 14-year observations, despite all global solar changes over the course of 11 years, showed no major temperature changes for the inner corona particles that generate the solar wind.
“Whatever heats most of the corona and solar wind doesn’t depend very much on the sun’s cycle of activity,” said Benjamin Boe, a University of Hawaii solar researcher involved in the new research, in a NASA statement that describes the study.
“The temperature at the sources of solar wind in the corona is almost constant during a solar cycle,” Habbal said in the statement. “This finding is unexpected because coronal structures are driven by changes in the distribution of magnetized plasmas in the corona that vary so widely during the 11-year solar magnetic cycle.”
To solve this new puzzle, according to NASA, the researchers plan to continue tracking total solar eclipses in the future for more observations. The next total solar eclipse will occur over Antarctica in December.
Follow Doris Elin Urrutia on Twitter @salazar_elin. Follow us on Twitter @Spacedotcom and on Facebook.